One thing that I was taught by an old person who use to repair a lot of stuff where I worked was you should drill a small hole at each end of the crack. This stops the crack from continuing out of the weld.

If you look at many of the welds on your truck, you will see places that it looks like the weld was not finished. The reason being if the weld does start to crack, the crack will stop where the gap in the weld is and not go all the way around the welded part. I learned this from a person that I worked for as a kid building frames for Double A fuel dragsters.